Integrated circuits have evolved into complex devices that include millions of transistors, capacitors and resistors on a single chip. The evolution of chip design results in faster circuitry and greater circuit density. As the demand for integrated circuits continues to rise, chip manufactures have demanded semiconductor process tooling having increased wafer throughput, greater product yield, and more robust processing equipment. To meet demands, tooling is being developed to minimize wafer handoff errors, reduce particle contamination, and increase the service life of tool components.
Lift pins are typically used in the semiconductor process tooling, such as a processing chamber, to support a substrate. The lift pins generally reside in guide holes disposed through the substrate support disposed within the processing chamber. The upper ends of the lift pins are typically flared to prevent the pins from passing through the guide holes. The lower ends of the lift pins extend below the substrate support and are actuated by a lift plate that contacts the pins at their lower ends. The lift plate is movable in a vertical direction between upper and lower positions. In the upper position, the lift plate moves the lift pins through the guide holes formed through the substrate support to extend the flared ends of the lift pins above the substrate support, thereby lifting the substrate into a spaced apart relation relative to the substrate support to facilitate substrate transfer.
It has been observed that current lift pin designs would cause high temperature spots (hot spots) on the substrate surface at regions where the lift pins are located. Hot spots on substrate may occur due to the absence of direct substrate support in the guide hole areas, which results in a larger gap between the substrate and lift pin and thus reduces dissipation of radiation heat coming from plasma. Radiation heat from plasma also increases lift pin temperature that causes hot spots on the substrate surface. These hot spots negatively affect the deposition rate localized above the lift pins. As a result, the uniformity of film thickness is suffered.
Therefore, there is a need in the art for an improved lift pin assembly.